US7667721B2 - Gray-scale improvement circuit and display system - Google Patents
Gray-scale improvement circuit and display system Download PDFInfo
- Publication number
- US7667721B2 US7667721B2 US11/587,695 US58769506A US7667721B2 US 7667721 B2 US7667721 B2 US 7667721B2 US 58769506 A US58769506 A US 58769506A US 7667721 B2 US7667721 B2 US 7667721B2
- Authority
- US
- United States
- Prior art keywords
- gray
- scale
- video signal
- conversion characteristic
- conversion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related, expires
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/20—Circuitry for controlling amplitude response
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/147—Scene change detection
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/06—Adjustment of display parameters
- G09G2320/0613—The adjustment depending on the type of the information to be displayed
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/06—Adjustment of display parameters
- G09G2320/066—Adjustment of display parameters for control of contrast
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/10—Special adaptations of display systems for operation with variable images
- G09G2320/103—Detection of image changes, e.g. determination of an index representative of the image change
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2340/00—Aspects of display data processing
- G09G2340/06—Colour space transformation
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2360/00—Aspects of the architecture of display systems
- G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
- G09G5/02—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed
Definitions
- the present invention relates to a gray-scale improvement circuit.
- the present invention also relates to a display system having a gray-scale improvement circuit and a display means such as a liquid crystal display.
- known gray-scale correction circuits divide the screen into a plurality of areas, calculate the mean value of the luminance signal in each area, create a luminance histogram of the mean luminance values in the areas, and control the input-output characteristic of a gray-scale correction means according to the luminance histogram (e.g., Patent Document 1).
- Patent Document 1 Japanese Patent Application Publication No. 2004-023522 (paragraph 0011, FIGS. 1 and 2)
- An object of the present invention is to increase contrast regardless of image content, and speed up response to changes in the image content.
- the present invention provides
- a gray-scale improvement circuit comprising:
- a gray-scale conversion means for receiving an input video signal, converting its gray scale as necessary, and outputting the video signal with the converted gray scale
- a statistical processing means for detecting a statistical property of each field or each frame of the input video signal
- a scene change detection means for detecting scene changes in the input video signal
- a conversion characteristic determination means for determining a gray-scale conversion characteristic from outputs of the statistical processing means and the scene change detection means
- the gray-scale conversion means converts the gray scale by using the gray-scale conversion characteristic determined by the conversion characteristic determination means.
- the present invention increases contrast regardless of image content, and enables faster response to changes in image content.
- FIG. 1 is a block diagram illustrating a gray-scale improvement circuit in a first embodiment of the invention.
- FIG. 2 is a graph showing conversion characteristics of the first gray-scale converter in the first embodiment of the invention.
- FIG. 3 is a graph showing conversion characteristics of the second gray-scale converter in the first embodiment of the invention.
- FIG. 4 is a graph showing an exemplary output result of the statistical processing means in the first embodiment of the invention.
- FIG. 5 is a graph showing another exemplary output result of the statistical processing means in the first embodiment of the invention.
- FIG. 6 is a graph showing another exemplary output result of the statistical processing means in the first embodiment of the invention.
- FIG. 7 is a graph showing another exemplary output result of the statistical processing means in the first embodiment of the invention.
- FIG. 8 shows an exemplary division of the screen by the scene change detection means in the first embodiment of the invention.
- FIG. 9 is a graph showing conversion characteristics of the first gray-scale converter in the first embodiment of the invention.
- FIG. 10 is a graph showing conversion characteristics of the second gray-scale converter in the first embodiment of the invention.
- FIG. 11 is a block diagram illustrating a gray-scale improvement circuit in a second embodiment of the invention.
- FIG. 12 is a graph showing conversion characteristics of the first gray-scale converter in the first color difference signal gray-scale conversion means in the second embodiment of the invention.
- FIG. 13 is a graph showing conversion characteristics of the second gray-scale converter in the first color difference signal gray-scale conversion means in the second embodiment of the invention.
- FIG. 14 is a block diagram showing details of the statistical processing means in the second embodiment of the invention.
- FIG. 15 is a block diagram illustrating a gray-scale improvement circuit in a third embodiment of the invention.
- FIG. 16 is a diagram showing the structure of a display system in a fourth embodiment of the invention, incorporating a gray-scale improvement circuit.
- 10 gray-scale conversion means 11 first gray-scale converter, 12 second gray-scale converter, 13 statistical processing means, 14 first target conversion characteristic setter, 15 second target conversion characteristic setter, 16 scene change detection means, 17 first applied conversion characteristic determiner, 18 second applied conversion characteristic determiner, 20 target conversion characteristic setting means, 22 applied conversion characteristic determination means, 24 conversion characteristic determination means, 31 gray-scale improvement circuit, 32 driving circuit, 33 display device, 34 display system, 100 input terminal, 200 output terminal, 300 input terminal.
- FIG. 1 shows a gray-scale improvement circuit according to a first embodiment of the present invention.
- the gray-scale improvement circuit shown in FIG. 1 receives an interlaced digital video signal as input, and outputs it with an improved gray scale.
- the video signal is a monochrome signal.
- this gray-scale improvement circuit has a gray-scale conversion means 10 that receives an input video signal, alters its gray-scale characteristic as necessary, and outputs the video signal with the converted gray-scale characteristic.
- the gray-scale conversion means 10 comprises a first gray-scale converter 11 and a second gray-scale converter 12 connected in cascade.
- the gray-scale improvement circuit in FIG. 1 further comprises a statistical processing means 13 that detects statistical properties of each field or each frame of the input video signal, a first target conversion characteristic setter 14 that determines a target conversion characteristic for the first gray-scale converter 11 from the output of the statistical processing means 13 , a second target conversion characteristic setter 15 that likewise determines a target conversion characteristic for the second gray-scale converter 12 from the output of the statistical processing means 13 , a scene change detection means 16 that detects scene changes in the input video signal, a first applied conversion characteristic determiner 17 that determines the conversion characteristic to be applied by the first gray-scale converter 11 from the output of the first target conversion characteristic setter 14 and the output of the scene change detection means 16 , and a second applied conversion characteristic determiner 18 that determines the conversion characteristic to be applied by the second gray-scale converter 12 from the output of the second target conversion characteristic setter 15 and the output of the scene change detection means 16 .
- a statistical processing means 13 that detects statistical properties of each field or each frame of the input video signal
- the first gray-scale converter 11 generates output by applying one of the five conversion characteristics (input-output characteristics) numbered 0 - 4 in FIG. 2 ; a signal output from the first applied conversion characteristic determiner 17 determines or specifies which of the conversion characteristics to use, as described later.
- the constants ks, ka 0 to ka 4 , and kc 1 to kc 4 are also selected so that when the input IN has its maximum value INmax, the output OUT will have its maximum value OUTmax.
- the plurality of conversion characteristics numbered 0 to 4 are characterized in that the higher the number is, the more intense a certain feature, namely the contrast in non-dark portions of the image, becomes. Therefore, for images having fewer dark portions, an image with heightened contrast and an improved gray-scale can be obtained by selecting conversion characteristics with higher numbers.
- the numbers in the drawing are also referred to as ‘characteristic numbers’ or ‘conversion characteristic specification values’ in this application.
- the second gray-scale converter 12 generates output by applying one of the five conversion characteristics (input-output characteristics) numbered 0 to 4 in FIG. 3 .
- a signal output from the second applied conversion characteristic determiner 18 determines or specifies which of the conversion characteristics to use, as will be described below.
- the constants kg, kd, and kb 0 to kb 4 are also selected so that when the input IN has its maximum value INmax, the output OUT will have its maximum value OUTmax.
- the plurality of conversion characteristics numbered 0 to 4 are characterized in that the higher the number is, the more intense a certain feature, namely the contrast in non-bright portions of the image, becomes. Therefore, for an image with fewer bright portions, an image with heightened contrast and an improved gray-scale can be obtained by selecting a conversion characteristic with a higher number.
- the numbers in the drawing are also referred to as the ‘characteristic numbers’ or ‘conversion characteristic specification values’ in this application.
- the statistical processing means 13 calculates a histogram for each field interval, that is, for each field. Specifically, the statistical processing means 13 classifies the pixel values of the input video signal (signal levels) into ten classes (0 to 9), and calculates the proportion of the pixels in each field belonging to each class to determine the frequency of appearance of each class.
- a histogram in which there are no significant differences in the frequency of appearance of different classes is obtained as shown in FIG. 4 .
- a histogram in which the higher signal level classes have a higher frequency of appearance is obtained as shown in FIG. 5
- a histogram in which the lower signal level classes have a higher frequency of appearance is obtained as shown in FIG. 6 .
- a histogram in which the middle signal level classes have the highest frequency of appearance is obtained as shown in FIG. 7 .
- the first target conversion characteristic setter 14 determines a class at which the cumulative frequency equals or exceeds a predetermined value, the cumulative frequency being calculated by accumulating the frequency of appearance of the classes from the class at the bottom of the gray scale (class 0) on up in ascending order (classes 1, 2, 3, . . . ), and sets a target conversion characteristic for the first gray-scale converter 11 according to the class thus determined. For example, the first target conversion characteristic setter 14 compares the output of the statistical processing means 13 with a predetermined value L and determines the target conversion characteristic specification value TC 1 for the first gray-scale converter 11 from the result of the comparison.
- the scene change detection means 16 compares the video signal of an input field or frame to the video signal of the preceding field or frame, and outputs a signal indicating the degree of the change in the video signal between the two fields or two frames as scene change information. For example, the scene change detection means 16 divides one screen into a plurality of areas, calculates the mean values of the pixels in the respective areas, and outputs the number of areas whose mean values differ by a predetermined value or more between fields as scene change information.
- one screen is partitioned into twenty-five areas (five parts horizontally and five parts vertically) as shown in FIG. 8 ; for each area in each field, the difference between the mean pixel value and the mean pixel value of the same area in the preceding field is calculated; the difference in mean values is compared with a predetermined value S; and a signal indicating the number of areas in which the mean value difference is equal to or greater than the predetermined value S is output as scene change information.
- the first applied conversion characteristic determiner 17 determines and outputs the conversion characteristic specification value FC 1 ( t ) of the conversion characteristic to be applied according to the target conversion characteristic specification value TC 1 obtained from the first target conversion characteristic setter 14 .
- the first applied conversion characteristic determiner 17 retains the conversion characteristic specification value FC 1 ( t ⁇ 1) applied in the preceding field, however, and bases its determination of the conversion characteristic specification value FC 1 ( t ) applied to the current field on FC 1 ( t ⁇ 1).
- the change (difference in specification value) from the conversion characteristic specification value FC 1 ( t ⁇ 1) applied in the preceding field is restricted to within a predetermined limit and the conversion characteristics specification value FC 1 ( t ) to be applied in the current field is set as close to the target conversion characteristic specification value TC 1 as possible within that limit.
- the value of the predetermined limit varies, however, depending on the output of the scene change detection means 16 .
- the change is unrestricted when the output SC from the scene change detection means 16 is twenty or more, the change is restricted to ⁇ 2 when SC is ten or more but less than twenty, and the change is restricted to ⁇ 1 when SC is less than ten.
- the target conversion characteristic specification value TC 1 is output as the applied conversion characteristic specification value FC 1 ( t ) without change.
- the change from the conversion characteristic specification value FC 1 ( t ⁇ 1) applied in the preceding field is limited to not more than ⁇ 2.
- the change from the conversion characteristic specification value FC 1 ( t ⁇ 1) applied in the preceding field is limited to not more than ⁇ 1.
- the value thus determined is output as the conversion characteristic specification value FC 1 ( t ) that applies in the current field.
- the first gray-scale converter 11 selects one of the conversion characteristics shown in FIG. 2 depending on the given applied conversion characteristic specification value FC 1 ( t ).
- the conversion characteristic indicated by the number equal to the given applied conversion characteristic specification value FC 1 ( t ) is selected. That is, when the applied conversion specification value FC 1 ( t ) is 0, 1, 2, 3, or 4, the selected conversion characteristic is number 0, 1, 2, 3, or 4, respectively.
- the second target conversion characteristic setter 15 determines a class at which the cumulative frequency equals or exceeds a predetermined value, the cumulative frequency being calculated by accumulating the frequency of appearance of the classes from the class at the top of the gray scale (class 9) on down in descending order (classes 8, 7, 6, . . . ) and sets a target conversion characteristic for the second gray-scale converter 12 according to the class thus determined.
- the second target conversion characteristic setter 15 compares the output of the statistical processing means 13 with a predetermined value H and determines the target conversion characteristic specification value TC 2 of the second gray-scale converter 12 from the result of the comparison.
- the second applied conversion characteristic determiner 18 determines and outputs the conversion characteristic specification value FC 2 ( t ) of the conversion characteristic to be applied according to the target conversion characteristic specification value TC 2 obtained from the second target conversion characteristic setter 15 .
- the second applied conversion characteristic determiner 18 retains the conversion characteristic specification value FC 2 ( t ⁇ 1) applied in the preceding field, however, and bases its determination of the conversion characteristic specification value FC 2 ( t ) applied to the current field on FC 2 ( t ⁇ 1).
- the change (difference in specification value) from the conversion characteristic specification value FC 2 ( t ⁇ 1) applied in the preceding field is restricted to within a predetermined limit and the conversion characteristics specification value FC 2 ( t ) to be applied in the current field is set as close to the target conversion characteristic specification value TC 1 as possible within that limit.
- the value of the predetermined limit varies, however, depending on the output of the scene change detection means 16 .
- the change is unrestricted when the output SC from the scene change detection means 16 is twenty or more, the change is restricted to ⁇ 2 when SC is ten or more but less than twenty, and the change is restricted to ⁇ 1 when SC is less than ten.
- the target conversion characteristic specification value TC 2 is output as the applied conversion characteristic specification value FC 2 ( t ) without change.
- the change from the conversion characteristic specification value FC 2 ( t ⁇ 1) applied in the preceding field is limited to not more than ⁇ 2.
- the change from the conversion characteristic specification value FC 2 ( t ⁇ 1) applied in the preceding field is limited to not more than ⁇ 1.
- the value thus determined is output as the conversion characteristic specification value FC 2 ( t ) that applies in the current field.
- the second gray-scale converter 12 selects one of the conversion characteristics shown in FIG. 3 depending on the given applied conversion characteristic specification value FC 2 ( t ).
- the conversion characteristic indicated by the number equal to the given applied conversion characteristic specification value FC 2 ( t ) is selected. That is, when the applied conversion specification value FC 2 ( t ) is 0, 1, 2, 3, or 4, the selected conversion characteristic is number 0, 1, 2, 3, or 4, respectively.
- the gray-scale characteristic is improved according to the content of the input video signal, a favorable improvement can be carried out without having flicker sensed when the gray scale is changed, and without loss of gray level resolution at the black or white end of the scale due to slow control response.
- the first target conversion characteristic setter 14 and the second target conversion characteristic setter 15 constitute a target conversion characteristic setting means that sets target conversion characteristics for the gray-scale conversion means 10 based on the output from 13 .
- the first applied conversion characteristic determiner 17 and the second applied conversion characteristic determiner 18 constitute an applied conversion characteristic determination means 22 that determines the conversion characteristic actually applied to the current field or frame from the target conversion characteristic set by the target conversion characteristic setting means 20 , the output of the scene change detection means 16 , and the conversion characteristic applied by the gray-scale conversion means 10 to the video signal in the preceding field or frame.
- the target conversion characteristic setting means 20 and applied conversion characteristic determination means 22 constitute a conversion characteristic determination means 24 that determines the conversion characteristic applied by the gray-scale conversion means 10 from the outputs of the statistical processing means 13 and scene change detection means 16 .
- the first gray-scale converter 11 and the second gray-scale converter 12 can select one of five conversion characteristics, but the number of conversion characteristic options is not limited to five; it may be more or less than five.
- gray-scale conversion means In the first embodiment, two gray-scale conversion means, two target conversion characteristic setting means, and two applied conversion characteristic determination means are provided in the gray-scale conversion means, but the invention is not limited to this configuration.
- the gray-scale conversion means may have only one of each of these means, although the improvement effect is then reduced.
- the exemplary statistical processing means 13 in the first embodiment calculates a histogram, but the target conversion characteristic specification value output by the first target conversion characteristic setter 14 may instead be found from the minimum value in the field, and the target conversion characteristic specification value output by the second target conversion characteristic setter 15 may be found from the maximum value in the field.
- the statistical processing means 13 may calculate the mean value of the field, and the target conversion characteristic specification value output by the first target conversion characteristic setter 14 may be found from the mean value. Less hardware is required to calculate the minimum, maximum, and mean values of a field than to calculate a histogram.
- target conversion characteristic specification value TC 1 from the minimum value.
- one of the characteristics shown in FIG. 9 will be selected according to the minimum value.
- the value can be selected as follows.
- the minimum value will be denoted MIN.
- TC 1 Predetermined values MIN 1 , MIN 2 , MIN 3 , MIN 4 , and MIN 5 satisfying the following condition are used: 0 ⁇ MIN1 ⁇ MIN2 ⁇ MIN3 ⁇ MIN4 ⁇ MIN5
- MAX target conversion characteristic specification value
- MAX 1 , MAX 2 , MAX 3 , MAX 4 , and MAX 5 satisfying the following condition are used: INmax>MAX1>MAX2>MAX3>MAX4>MAX5 where INmax is the maximum value that the input video signal can take.
- INmax is the maximum value that the input video signal can take.
- INmax is 255.
- TC 1 target conversion characteristic specification value
- AVE target conversion characteristic specification value
- TC 1 Predetermined values AVE 0 , AVE 1 , AVE 2 , AVE 3 , AVE 4 , and AVE 5 satisfying the following condition are used: AVE0 ⁇ AVE1 ⁇ AVE2 ⁇ AVE3 ⁇ AVE4 ⁇ AVE5.
- the conversion characteristics correspond to characteristic numbers and are selected by specifying their characteristic numbers.
- the conversion characteristics may be alterable in a continuous fashion without steps.
- the conversion characteristic is altered by changing one of its parameters: for example, by changing a constant in the mathematical expression representing the conversion characteristic, or changing the range to which the expression applies. That is, one of the constants ks, ka 1 , ka 0 to ka 4 , kc 1 to kc 4 , kb 0 to kb 4 , kg, and kd may be altered, or one of the values IN 11 to IN 14 and IN 21 to IN 24 that indicate the applicable range of the characteristic line given by the above expressions (1) to (6) and (8) to (13) may be altered.
- the target conversion characteristic setters 14 , 15 do not generate target conversion characteristic specification values corresponding to a characteristic number; instead, they generate a parameter (a value which represents a constant or the applicable range of an expression) defining a conversion characteristic, and thereby specify the conversion characteristic.
- the video signal is a monochrome signal.
- the video signal is a color signal
- separate gray-scale conversion means may be provided for each component of the color signal and gray-scale conversion may be carried out each signal component separately.
- the gray-scale improvement circuit is configured as shown, for example, in FIG. 11 .
- the gray-scale improvement circuit in FIG. 11 is similar to the circuit in FIG. 1 except for the following points.
- the gray-scale conversion means 10 in FIG. 11 has a luminance signal gray-scale conversion means 10 y that converts the gray scale of the luminance signal, and color difference signal gray-scale conversion means 10 r , 10 b that convert the gray scale of the first and second color difference signals in the video signal.
- the luminance signal gray-scale conversion means 10 y includes a first gray-scale converter 11 y and a second gray-scale converter 12 y connected in cascade, similar to the first gray-scale converter 11 and second gray-scale converter 12 in FIG. 1 .
- the first color difference signal gray-scale conversion means 10 r (the Cr signal gray-scale conversion means) includes a first gray-scale converter 11 r and a second gray-scale converter 12 r connected in cascade.
- the second color difference signal gray-scale conversion means 10 b (the Cb signal gray-scale conversion means) includes a first gray-scale converter 11 b and a second gray-scale converter 12 b connected in cascade.
- the conversion characteristics of the first gray-scale converter 11 r in the Cr signal gray-scale conversion means 10 r are shown in FIG. 12 .
- the color difference signal Cr takes on both positive and negative values, so the conversion characteristics of the first gray-scale converter 11 r include a range in which the input is positive and a range in which the input is negative.
- the conversion characteristics in the positive range are similar to those of the first gray-scale converter 11 y in the luminance signal gray-scale conversion means 10 y .
- the conversion characteristics in the negative range are substantially point symmetric to the characteristics in the positive range with the origin as the center of symmetry.
- the values of INmax and OUTmax in the positive range are half of the values for the luminance signal. If the luminance signal takes on values from 0 to 255, the first color difference signal Cr takes on values from ⁇ 128 to 127.
- the parameters of the mathematical expressions representing the characteristics in particular the parameters (kc 1 , kc 2 , kc 3 , kc 4 ) corresponding to the intercept on the vertical axis or output axis, are changed proportionally.
- the conversion characteristics of the first gray-scale converter 11 b in the Cb signal gray-scale conversion means 10 b are similar to the characteristics shown in FIG. 12 .
- the conversion characteristics of the second gray-scale converter 12 r in the Cr signal gray-scale conversion means 10 r are shown in FIG. 13 .
- the color difference signal Cr takes on both positive and negative values, so the conversion characteristics of the second gray-scale converter 12 r include a range in which the input is positive, and a range in which the input is negative.
- the conversion characteristics in the positive range are similar to those of the second gray-scale converter 12 y in the luminance signal gray-scale conversion means 10 y .
- the conversion characteristics in the negative range are substantially point symmetric to the characteristics in the positive range with the origin as the center of symmetry.
- the values of INmax and OUTmax in the positive range are half of the values for the luminance signal. If the luminance signal takes on values from 0 to 255, the first color difference signal Cr takes on values from ⁇ 128 to 127.
- the parameters of the mathematical expressions representing the characteristics including in particular the parameter (kb) corresponding to the intercept on the vertical axis or output axis, are changed proportionally.
- the conversion characteristics of the second gray-scale converter 12 b in the Cb signal gray-scale conversion means 10 b are similar to the characteristics shown in FIG. 13 .
- the first and second gray-scale conversion means in the luminance signal gray-scale conversion means 10 y , the Cr signal gray-scale conversion means 10 r , and the Cb signal gray-scale conversion means 10 b are controlled by the output from the applied conversion characteristic determination means 22 , and carry out gray-scale conversion using a conversion characteristic identified, for example, by a number equal to the specified value output from the applied conversion characteristic determination means 22 .
- the gray-scale improvement circuit in FIG. 11 includes a video signal conversion means 26 that converts the input video signal containing a luminance signal and color difference signals to red, blue, and green color signals.
- the statistical processing means 13 calculates histograms for the red, blue, and green color signals output from the video signal conversion means 26 as shown in FIG. 14 .
- the statistical processing means 13 comprises a red signal statistical processing means 13 R, a green signal statistical processing means 13 G, and a blue signal statistical processing means 13 B that calculate histograms for the red, green, and blue signals, respectively, and a totalizing means 13 S that totals these statistical quantities.
- the totalizing means 13 S carries out weighted addition of the statistical quantities from the red signal statistical processing means 13 R, green signal statistical processing means 13 G, and blue signal statistical processing means 13 B to generate a final result (the result of statistical processing).
- the red and blue signals may be given smaller weights than the highly visible green signal.
- the statistical processing can be performed on the luminance signal and color difference signals without converting them to red, green, and blue color signals.
- the input video signal comprises a luminance signal (Y) and two color difference signals (Cr, Cb). If the input video signal includes red, green, and blue color signals, the gray-scale improvement circuit may be structured as in FIG. 15 , for example.
- the gray-scale improvement circuit of FIG. 15 is similar to that in FIG. 1 except for the following points.
- the gray-scale conversion means 10 in FIG. 15 has a red signal gray-scale conversion means 10 R which converts the gray scale of the red color signal in the video signal, a green signal gray-scale conversion means 10 G which converts the gray scale of the green color signal, and a blue signal gray-scale conversion means 10 B which converts the gray scale of the blue color signal.
- the gray-scale conversion means 10 R, 10 G, 10 B have respective first gray-scale converters 11 R, 11 G, 11 B and second gray-scale converters 12 R, 12 G, 12 B connected in cascade, similar to the first gray-scale converter 11 and second gray-scale converter 12 in FIG. 1 .
- the red signal gray-scale conversion means 10 R, green signal gray-scale conversion means 10 G, and blue signal gray-scale conversion means 10 B are all similar and are controlled by the output from the applied conversion characteristic determination means 22 to carry out gray-scale conversion using a conversion characteristic identified by, for example, a number equal to the specified value output from the applied conversion characteristic determination means.
- the gray-scale improvement circuit in FIG. 15 includes a video signal conversion means 28 that converts the input video signal comprising red, green, and blue color difference signals to a luminance signal; the scene change detection means 16 calculates statistics of the luminance signal output from the video signal conversion means 28 .
- scene changes are detected between fields, but they may be detected between frames.
- a field-to-field limit is placed on the control values in the gray-scale conversion means 11 , 12 on the assumption that the input signal is for an interlaced video signal, but this is not a limitation; if the input signal is a progressive video signal, a frame-to-frame limit can be placed on the control values and scene changes can be detected between frames to achieve similar effects.
- the gray-scale improvement circuits described in the above embodiments manipulate the gray-scale conversion characteristic according to a statistical property of the video signal and limit the amount of change in the gray-scale conversion characteristic from field to field or frame to frame, but relax this limit at scene changes.
- the circuit can follow changes in image content without delay, and an improved video signal always having high contrast can be obtained.
- the scene change detection means comprises an areal mean value detection means that divides one screen into a plurality of areas and calculates a mean value for one field or one frame interval for each area.
- the number of areas in which the difference in the mean value between fields or frames is equal to or greater than a predetermined value is used as scene change information, enabling scene changes to be detected correctly with only a small amount of hardware.
- a display system can be constructed by combining the gray-scale improvement circuit described in the first embodiment with a display means.
- FIG. 16 shows an example of this kind of display system.
- the display system 34 shown in FIG. 16 comprises a gray-scale improvement circuit 31 , a driving circuit 32 , and a display device 33 .
- any of circuits described in the first, second, and third embodiments above, for example, can be used for the gray-scale improvement circuit 31 .
- the driving circuit 32 drives the display device 33 according to the output from the gray-scale improvement circuit 31 .
- a video signal input at the input terminal 300 is input to the gray-scale improvement circuit 31 , its gray scale is improved as described in the first, second, or third embodiment, and the improved video signal is input to the driving circuit 32 .
- the driving circuit 32 converts it into a signal for driving the display device 33 , and supplies the converted signal to the display device 33 .
- the display device 33 displays an image responsive to the output of the driving circuit 32 .
- any display means can be used; examples include a liquid crystal panel, PDP (plasma display panel), DMD (digital micromirror device) panel, LCoS (Liquid Crystal on Silicon, a reflective liquid crystal panel), CRT (cathode ray tube), and FED (field emission display) panel.
- PDP plasma display panel
- DMD digital micromirror device
- LCoS Liquid Crystal on Silicon
- CRT cathode ray tube
- FED field emission display
- the display system comprises a gray-scale improvement circuit, an improved video signal always having high contrast is obtained.
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Picture Signal Circuits (AREA)
- Image Processing (AREA)
Abstract
Description
OUT=ka0·IN (ka0 being a constant) (1)
OUT=ks·IN (ks being a constant) (2)
and when the input IN is greater than the value IN11, the relationship of the output to the input IN is expressed as
OUT=ka1·IN+kc1 (ka1 and kc1 being constants) (3)
(When the input IN is equal to the above value IN11, both equations (2) and (3) are satisfied.)
OUT=ka2·IN+kc2 (ka2 and kc2 being constants) (4)
(When the input IN is equal to the above value IN12, both equations (2) and (4) are satisfied.)
OUT=ka3·IN+kc3 (ka3 and kc3 being constants) (5)
(When the input IN is equal to the above value IN13, both equations (2) and (5) are satisfied.)
OUT=ka4·IN+kc4 (ka4 and kc4 being constants) (6)
(When the input IN is equal to the above value IN14, both equations (2) and (6) are satisfied.)
ks<ka0<ka1<ka2<ka3<ka4 (7)
IN14−IN13=IN13−IN12=IN12−IN11=IN11
so that when the value of the characteristic number changes by one, in the associated gray-scale conversion characteristic, the strength of the above feature changes by a corresponding amount.
OUT=kb0·IN (kb0 being a constant) (8)
OUT=kg·IN+kd (kg and kd being constants) (9)
and when the input IN is less than the value IN21, the relationship of the output to the input IN is expressed as
OUT=kb1·IN (kb1 being a constant) (10)
(When the input IN is equal to the above value IN21, both equations (9) and (10) are satisfied.)
OUT=kb2·IN (kb being a constant) (11)
(When the input IN is equal to the above value IN22, both equations (9) and (11) are satisfied.)
OUT=kb3·IN (kb3 being a constant) (12)
(When the input IN is equal to the above value IN23, both equations (9) and (12) are satisfied.)
OUT=kb4·IN (kb4 being a constant) (13)
(When the input IN is equal to the above value IN24, both equations (9) and (13) are satisfied.)
kg<kb0<kb1<kb2<kb3<kb4 (14)
INmax−IN21=IN21−IN22=IN22−IN23=IN23−IN24
so that when the value of the characteristic number changes by one, in the associated gray-scale conversion characteristic, the strength of the above feature changes by a corresponding amount.
if L≦L1, then TC1=0,
if L1<L≦L1+L2, then TC1=1,
if L1+L2<L≦L1+L2+L3, then TC1=2,
if L1+L2+L3<L≦L1+L2+L3+L4, then TC1=3, and
if L1+L2+L3+L4<L, then TC1=4.
if H≦H1, then TC2=0,
if H1<H≦H1+H2, then TC2=1,
if H1+H2<H≦H1+H2+H3, then TC2=2,
if H1+H2+H3<H≦H1+H2+H3+H4, then TC2=3, and
if H1+H2+H3+H4<H, then TC2=4.
0<MIN1<MIN2<MIN3<MIN4<MIN5
The value of TC1 is determined as follows:
if 0≦MIN<MIN1, then TC1=0,
if MIN1≦MIN<MIN2, then TC1=11,
if MIN2≦MIN<MIN3, then TC1=2,
if MIN3≦MIN<MIN4, then TC1=3, and
if MIN4≦MIN<MIN5, then TC1=4.
INmax>MAX1>MAX2>MAX3>MAX4>MAX5
where INmax is the maximum value that the input video signal can take. When the input video signal is an eight-bit signal, INmax is 255. The value of TC2 is determined as follows:
if MAX1≦MIN<INmax, then TC2=0,
if MIN2≦MIN<MIN1, then TC2=1,
if MIN3≦MIN<MIN2, then TC2=2,
if MIN4≦MIN<MIN3, then TC2=3, and
if MIN5≦MIN<MIN4, then TC2=4.
AVE0<AVE1<AVE2<AVE3<AVE4<AVE5.
The value of TC1 is determined as follows:
if AVE0≦AVE<AVE1, then TC1=0,
if AVE1≦AVE<AVE2, then TC1=1,
if AVE2≦AVE<AVE3, then TC1=2,
if AVE3≦AVE<AVE4, then TC1=3, and
if AVE4≦AVE<AVE5, then TC1=4.
Claims (10)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2004-132842 | 2004-04-28 | ||
JP2004132842A JP3698710B1 (en) | 2004-04-28 | 2004-04-28 | Gradation improvement circuit and display system |
PCT/JP2005/002285 WO2005107238A1 (en) | 2004-04-28 | 2005-02-16 | Gradation improving circuit and display system |
Publications (2)
Publication Number | Publication Date |
---|---|
US20080062101A1 US20080062101A1 (en) | 2008-03-13 |
US7667721B2 true US7667721B2 (en) | 2010-02-23 |
Family
ID=35093850
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/587,695 Expired - Fee Related US7667721B2 (en) | 2004-04-28 | 2005-02-16 | Gray-scale improvement circuit and display system |
Country Status (4)
Country | Link |
---|---|
US (1) | US7667721B2 (en) |
JP (1) | JP3698710B1 (en) |
TW (1) | TWI264941B (en) |
WO (1) | WO2005107238A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080055482A1 (en) * | 2006-08-31 | 2008-03-06 | Canon Kabushiki Kaisha | Image processing apparatus and method |
US20130063666A1 (en) * | 2009-04-23 | 2013-03-14 | Canon Kabushiki Kaisha | Image processing apparatus and image processing method for performing correction processing on input video |
US20140368558A1 (en) * | 2013-06-14 | 2014-12-18 | Canon Kabushiki Kaisha | Image display apparatus and method of controlling same |
US10804395B2 (en) | 2014-08-22 | 2020-10-13 | Taiwan Semiconductor Manufacturing Company, Ltd. | Metal-insensitive epitaxy formation |
US11935951B2 (en) | 2014-08-22 | 2024-03-19 | Taiwan Semiconductor Manufacturing Company, Ltd. | Metal-insensitive epitaxy formation |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPWO2007145168A1 (en) * | 2006-06-13 | 2009-10-29 | パナソニック株式会社 | Tone correction device |
KR100843090B1 (en) | 2006-10-25 | 2008-07-02 | 삼성전자주식회사 | Apparatus and method for improving a flicker for images |
US20080122857A1 (en) * | 2006-11-29 | 2008-05-29 | Chih-Lin Hsuan | Methods and devices for adjusting display characteristic of a video frame according to luminance statistics |
KR101359920B1 (en) * | 2007-04-03 | 2014-02-12 | 포항공과대학교 산학협력단 | Driving apparatus for display device, display device including the same and driving method of display device |
US8605019B2 (en) * | 2008-09-30 | 2013-12-10 | Sharp Kabushiki Kaisha | Display device and display device driving method, and display driving control method |
EP2537138B1 (en) | 2010-02-19 | 2014-04-02 | Thomson Licensing | Parameters interpolation for high dynamic range video tone mapping |
Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0799619A (en) | 1993-05-24 | 1995-04-11 | Sony Corp | Image processor |
JP2000069327A (en) | 1998-08-24 | 2000-03-03 | Matsushita Electric Ind Co Ltd | Gamma-correction device |
US6388678B1 (en) * | 1997-12-10 | 2002-05-14 | Matsushita Electric Industrial Co., Ltd. | Plasma display panel drive pulse controller |
JP2002185817A (en) | 2000-12-19 | 2002-06-28 | Matsushita Electric Ind Co Ltd | Video signal processing method and video signal processing unit |
JP2002320111A (en) | 2001-04-23 | 2002-10-31 | Matsushita Electric Ind Co Ltd | Gradation correcting device |
JP2002359754A (en) | 2001-05-31 | 2002-12-13 | Matsushita Electric Ind Co Ltd | Grey level correction device and method |
US20030011545A1 (en) * | 2001-06-14 | 2003-01-16 | Canon Kabushiki Kaisha | Image display apparatus |
JP2003219205A (en) | 2002-01-24 | 2003-07-31 | Sony Corp | Image pickup device, display device, image recorder and method for correcting image quality |
JP2004007301A (en) | 2002-06-03 | 2004-01-08 | Kddi Media Will Corp | Image processor |
JP2004007076A (en) | 2002-05-30 | 2004-01-08 | Mitsubishi Electric Corp | Video signal processing method and video signal processing apparatus |
JP2004023522A (en) | 2002-06-18 | 2004-01-22 | Sanyo Electric Co Ltd | Contrast correction circuit |
JP2004032551A (en) | 2002-06-27 | 2004-01-29 | Seiko Epson Corp | Image processing method, image processor, and projector |
-
2004
- 2004-04-28 JP JP2004132842A patent/JP3698710B1/en not_active Expired - Fee Related
-
2005
- 2005-02-16 WO PCT/JP2005/002285 patent/WO2005107238A1/en not_active Application Discontinuation
- 2005-02-16 US US11/587,695 patent/US7667721B2/en not_active Expired - Fee Related
- 2005-03-04 TW TW094106544A patent/TWI264941B/en not_active IP Right Cessation
Patent Citations (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0799619A (en) | 1993-05-24 | 1995-04-11 | Sony Corp | Image processor |
US6388678B1 (en) * | 1997-12-10 | 2002-05-14 | Matsushita Electric Industrial Co., Ltd. | Plasma display panel drive pulse controller |
JP2000069327A (en) | 1998-08-24 | 2000-03-03 | Matsushita Electric Ind Co Ltd | Gamma-correction device |
JP2002185817A (en) | 2000-12-19 | 2002-06-28 | Matsushita Electric Ind Co Ltd | Video signal processing method and video signal processing unit |
JP2002320111A (en) | 2001-04-23 | 2002-10-31 | Matsushita Electric Ind Co Ltd | Gradation correcting device |
JP2002359754A (en) | 2001-05-31 | 2002-12-13 | Matsushita Electric Ind Co Ltd | Grey level correction device and method |
US20030011545A1 (en) * | 2001-06-14 | 2003-01-16 | Canon Kabushiki Kaisha | Image display apparatus |
JP2003219205A (en) | 2002-01-24 | 2003-07-31 | Sony Corp | Image pickup device, display device, image recorder and method for correcting image quality |
JP2004007076A (en) | 2002-05-30 | 2004-01-08 | Mitsubishi Electric Corp | Video signal processing method and video signal processing apparatus |
JP2004007301A (en) | 2002-06-03 | 2004-01-08 | Kddi Media Will Corp | Image processor |
JP2004023522A (en) | 2002-06-18 | 2004-01-22 | Sanyo Electric Co Ltd | Contrast correction circuit |
JP2004032551A (en) | 2002-06-27 | 2004-01-29 | Seiko Epson Corp | Image processing method, image processor, and projector |
US20040032982A1 (en) * | 2002-06-27 | 2004-02-19 | Seiko Epson Corporation | Image processing method, image processing apparatus, and projector |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080055482A1 (en) * | 2006-08-31 | 2008-03-06 | Canon Kabushiki Kaisha | Image processing apparatus and method |
US9019433B2 (en) | 2006-08-31 | 2015-04-28 | Canon Kabushiki Kaisha | Image processing apparatus and method |
US20130063666A1 (en) * | 2009-04-23 | 2013-03-14 | Canon Kabushiki Kaisha | Image processing apparatus and image processing method for performing correction processing on input video |
US8654260B2 (en) * | 2009-04-23 | 2014-02-18 | Canon Kabushiki Kaisha | Image processing apparatus and image processing method for performing correction processing on input video |
US20140368558A1 (en) * | 2013-06-14 | 2014-12-18 | Canon Kabushiki Kaisha | Image display apparatus and method of controlling same |
US9773459B2 (en) * | 2013-06-14 | 2017-09-26 | Canon Kabushiki Kaisha | Image display apparatus that has a light emitting unit and method of controlling same |
US10804395B2 (en) | 2014-08-22 | 2020-10-13 | Taiwan Semiconductor Manufacturing Company, Ltd. | Metal-insensitive epitaxy formation |
US11495685B2 (en) | 2014-08-22 | 2022-11-08 | Taiwan Semiconductor Manufacturing Company, Ltd. | Metal-insensitive epitaxy formation |
US11935951B2 (en) | 2014-08-22 | 2024-03-19 | Taiwan Semiconductor Manufacturing Company, Ltd. | Metal-insensitive epitaxy formation |
Also Published As
Publication number | Publication date |
---|---|
TWI264941B (en) | 2006-10-21 |
WO2005107238A1 (en) | 2005-11-10 |
JP3698710B1 (en) | 2005-09-21 |
TW200541325A (en) | 2005-12-16 |
US20080062101A1 (en) | 2008-03-13 |
JP2005318198A (en) | 2005-11-10 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7667721B2 (en) | Gray-scale improvement circuit and display system | |
US9177514B2 (en) | Image display apparatus and image display method | |
JP3766274B2 (en) | Time-division color display device and display method | |
US7808462B2 (en) | Display apparatus | |
US20080069478A1 (en) | Apparatus, method, and computer program product for displaying image | |
US9406113B2 (en) | Image processing apparatus and image display apparatus | |
TWI222320B (en) | Signal processing unit and liquid crystal display device | |
US8155435B2 (en) | Display apparatus and its control method | |
US9734773B2 (en) | Display improvement method and apparatus for liquid crystal display panel | |
JPH05127620A (en) | Method and circuit for adjusting liquid crystal projection type color display | |
JP4701851B2 (en) | Image display apparatus and control method thereof | |
US7466298B2 (en) | Liquid crystal display device for improving a display response speed and driving method for the same | |
CN107342054B (en) | Display device, display control method and display control unit | |
US20120026208A1 (en) | Image display apparatus | |
CN108600719B (en) | Projection device and method for sensing ambient light brightness in real time | |
KR101336870B1 (en) | Method and apparatus to improve the visual perception of an image displayed on a screen | |
US9786038B2 (en) | Method for processing an image sequence having consecutive video images in order to improve the spatial resolution | |
US8743140B2 (en) | Color adjustment device, method for adjusting color and display for the same | |
CN114613315A (en) | Gamma curve learning method and LED display controller | |
CN110570824A (en) | Liquid crystal display, image display method thereof and backlight control device | |
JP4692435B2 (en) | Gradation improvement circuit and display system | |
WO2012099041A1 (en) | Image display device and image display method | |
CN114038379B (en) | Sub-pixel starting sequence determination method, sub-pixel starting method and pixel driving circuit | |
US11637964B2 (en) | Image processing apparatus, image display system, image processing method having a time dithering process | |
CN100524447C (en) | Display apparatus and its control method |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: MITSUBISHI ELECTRIC CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MINAMI, KOJI;SAKUWA, CHIHIRO;GAI, TOSHIHIRO;AND OTHERS;REEL/FRAME:018504/0566 Effective date: 20061013 Owner name: MITSUBISHI ELECTRIC CORPORATION,JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MINAMI, KOJI;SAKUWA, CHIHIRO;GAI, TOSHIHIRO;AND OTHERS;REEL/FRAME:018504/0566 Effective date: 20061013 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
FEPP | Fee payment procedure |
Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.) |
|
LAPS | Lapse for failure to pay maintenance fees |
Free format text: PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES (ORIGINAL EVENT CODE: EXP.) |
|
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
|
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 20180223 |